Certificate of correction



United States Patent 3,126,352 HYDRATED BORATE PRODUCTS Laurence R. Blair, Gillette, and Karlis L. Jaunarajs,

Somerville, N.J., assignors to J ulms-Manville Corporation, New York, N.Y., a corporation of New York No Drawing. Filed Dec. 31, 1958, Ser. No. 784,081 14 Claims. (Cl. 252-478) This invention relates to an improved shielding material or medium for noxious radiation, especially neutrons, and more particularly to an effective neutron absorbent boron material or composition which is self-bonding and may be molded or shaped separately or in combination with other neutron or gamma ray shielding material materials into handleable, mechanically self-supporting, structural shapes or bodies, or applied as cementitious or mortar-like materials.

Progress in the development and application of atomic reactors, cyclotrons and in related fields involving radio active materials, the increased utilization thereof, with the inherently noxious radioactive emanations produced thereby has brought about an urgent need for improved and more adaptable shielding materials or mediums for the protection of personnel and adjacent equipment from such noxious radiation. While noxious radioactive emanations, e.g., gamma rays, neutrons or the like, and radioactive shielding materials or mediums have long been known, understood and utilized, conventional shields comprising bulky masses of dense materials such as lead, concrete, steel, etc., present numerous obvious and inherent disadvantages. These conventional types of materials, in general, are of necessity, heavy, massive and bulky, lacking adaptability in many applications and convenient fabrication and/ or installation, and, notwithstanding such inherent disadvantages, frequently are not efiicient in attenuating or absorbing neutrons. Moreover, exposure of many typical shielding materials to radiation frequently induces radioactivity in the shielding material whereby the shield itself may disseminate noxious radiation, i.e., secondary radiation.

In many applications shields comprising massive and bulky high density structures are giving way to more efficient and practical protective structures consisting of effective neutron energy reducing and absorbing compositions such as high hydrogen and/ or boron containing materials alone or in combination with high density gamma radiation absorbing materials. Boron, of course, is an almost unique element insofar as slowing and capturing slow or thermal neutrons is concerned because of its ability to absorb large amounts of thermal neutrons while emitting only soft /2 m.e.v.) gamma rays and readily adsorbed alpha particles. United States Letters Patent No. 2,796,529 and No. 2,727,996, for example, fully describe several radiation shielding mediums or constructions embodying metallic boron or boron compounds dispersed discontinuously and uniformly throughout a supporting matrix such as synthetic resin or malleable metal. Such boron containing shielding mediums have included boron in a number of forms, such, for example, as elemental boron, natural borate minerals such as colemanite or borax, boric acid, boron organic compounds, synthetically produced boron carbide, boron alloys such as aluminum-boron carbide, aqueous solutions of boron salts and the like. These materials or their application in the prior art, however, almost without exception are subject to one or more material disadvantage. For example, among other reasons apparent to those skilled in the art, boron metal, boron carbide or the like are very expensive, many boron containing materials or compounds are not stable when subjected to elevated temperatures or exposed to moisture or oxidizing conditions and therefore require expensive or cumbersome waterproofing, and weatherproofing or the inexpensive and 3,125,352 Patented Mar. 24, 1964 "Ice stable boron compounds are not generally available in mechanically self-retaining or self-supporting structural and/or readily moldable forms and are therefore difficult to set into place around reactors, conduits, etc., without the use of a binder or supporting matrix. Typical bonding materials by themselves are not effective in shielding or absorbing radiation and their use may substantially reduce the boron content or density of a shielding medium and thereby necessitate the use of a heavier and/ or thicker shield to provide the high boron concentrations required. Moreover, radioactivity may be induced into some bonding materials whereby they become a secondary source of radiation.

A principal object of this invention is to provide an insoluble, heat resistant, inorganic self-bonding borate compound which may be molded or shaped into strong and handleable but workable, mechanically self-supporting, shape retaining structural bodies or units of substantially any configuration desired, and a method of preparing the same.

A further object of this invention is to provide an effective and efiicient shielding medium for noxious radioactive emanations comprising an insoluble, inorganic selfbonding neutron absorbing compound of relatively high borate content which may be shaped or molded into handleable, mechanically self-supporting, shape retaining structural bodies or units.

A further object of this invention is to provide a relatively low cost, water resistant, stable, self-bonding high capacity slow or thermal neutron absorbing borate shielding composition which may be provided as shape retaining mechanically self-supporting structural units or bodies, or as a plastic, cohesive mass with cementitious or mortar-like properties or characteristics, which upon drying results in a mecahnically self-supporting structural mass.

A further object of this invention is to provide a mechanically self-supporting structural borate shielding material or composition for slow or thermal neutrons which has a relatively low thermal conductivity, is stable at high temperatures and is an efficient and effective thermal insulation as well as a shielding absorbent for noxious radioactive emanations.

A still further object of this invention is to provide self-bonding, plastic, cohesive cementitious or mortar-like boron compositions which have neutron absorbing properties, are readily applicable, self-setting and low cost, and can be utilized to produce mechanically self-supporting, structural monolithic-like masses or mortar bonded joints which absorb neutrons and are water and heat resistant, stable, and eflicient thermal insulators.

This invention will be more fully understood and fur ther objects and advantages thereof will become apparent from a consideration of the following detailed description of the invention.

In general, the objects of this invention are obtained by a radiation shield, and thermal insulation, comprising a water insoluble gel precipitate or reaction product of an aqueous solution of borax with a soluble salt of a mineral or organic acid and a divalent metal from group H of the periodic table comprising calcium, barium, magnesium, cadmium, zinc and mixtures thereof, soluble salts of mineral or inorganic acids being preferred. Soluble salts of the foregoing divalent metals may be prepared from or comprise those of inorganic acids such as hydrochloric, nitric or sulfuric acid and mixtures thereof, or organic acids such as acetic, lactic, and the like, provided that the salts solubility is adequate, i.e., a solubility of at least approximately 1 part by weight of the salt per 3 parts by weight of water. The solubility of the reactants is material as pointed out hereinafter and very slightly soluble salts such as calcium sulfate are not satis factory. The relative amounts or ratios of borax and soluble divalent metal salts in the aqueous solution should be such as to provide, on an oxide basis, approximately 1-2 mols of B for each mol of divalent metal oxide. Formation or precipitation of the gel reaction product and the characteristics of said gel reaction product or precipitate are substantially enhanced by effecting the reaction at solution temperatures ranging from that approximating room temperatures (60-.-70 F.) up to about 200 F. The resultant insoluble reaction product or precipitate is a voluminous gel with cohesive self-bonding properties, and the precipitate must be gelatinous in nature in that crystalline precipitates, lacking cohesiveness or self-adherence, cannot be shaped, molded or otherwise provided as self-bonded, mechanically self-supporting, handleable structural bodies or shapes. Dewatering or consolidation of the resulting slurry of gel precipitate is typically desirable or even necessary, depending, of course, upon the concentration s) of the solution(s) containing the reactants, and, in turn, the water to solids ratio of the resulting gel precipitate slurry and the characteristics desired in the final product, e.g., whether or not the gel precipitate is to be shaped or molded into handleable structural units or poured like concrete and the desired density thereof. It should be understood, however, that dewatering or consolidation may be effected by substantially any conventional means such as compression molding, filtering or the like, and because of the large quantities of water typically present in the gel precipitate slurries notwithstanding the use of reactant solutions of maximum concentration, dewatering of the gel precipitate is usually necessary and preferred in the preparation of either shaped structural units or a plastic cohesive cement.

Formation of a gel precipitate and its characteristics, as indicated hereinbefore, are influenced by the solution temperatures. For example, effecting the formation of the gel precipitate at temperatures ranging between approximately 68 and 208 F. results in gel precipitate yields ranging between 80100% and a temperature of approximately 86 -F. results in about a maxirnum or approximately 100% yield. Thus, although reaction temperatures are significant and an optimum yield or recovery certainly desirable, other factors or considerations, in particular obtaining a sutficiently high solids to water ratio of the resulting gel precipitate slurry to permit practical and economical dewatering and forming a shaped products or a workable cement, are equally significant. In other words, the low solubility of some reactants, particularly borax, at low temperatures such as those which influence maximum precipitate yield, e.g., room temperatures up to approximately 100 F., generally produce reactive solutions which result in gel precipitate slurries having water to solids ratios too high for efficient, economical dewatering and/ or molding. Thus, to a point, the higher the temperature of the aqueous solvent the greater the amount of borax and/or soluble reactants soluble therein, and the greater the concentration of solids to water ratio which materially facilitates dewatering. Accordingly, it is to be understood that the preferred or optimum conditions for efiicient and economical practice of this invention are the result of a compromise between apparently contrary factors, i.e., the optimum temperature conditions for maximum precipitationv and the optimum tempertaure conditions for the maximum dissolution or maximum solids to water ratio of the solution. Moreover, it has also been found that the gel precipitates formed at higher temperatures generally have better filtering roperties. Typically preferred aqueous temperatures for dissolving reactants such as borax therefore comprise those ranging between about 120 to 190 F., preferably approximately 140 F. for the dissolution of borax, although it is to be understood that a suitable gel may be precipitated at temperatures ranging anywhere from about 60 to 210 F. High dissolution temperatures and subsequent cooling of the saturated solution prior to precipitation may be utilized, of course, as a means of attempting to achieve maximum efiiciency, but in accordanee with generally known principles, excessive cooling must be avoided and care taken to avoid premature precipitation of the reactive solute from the resulting supersaturated solution prior to the desired reaction. Borax being only slightly or moderately soluble, requires elevated temperatures, usually at least approximately 125 F. and preferably about 140 'F. to achieve a borax solution of sufficient concentration to result in an economical solids to water ratio, e.g., about 100 lbs. of borax to 50 gals. of water. Readily soluble materials such as calcium chloride may be added to cold water because of their greater solubility, and a cold solution thereof may be added to the borax solution without materially impeding the reaction because the resulting calcium borate gel precipitate removes borax from solution at a rapid rate preventing saturation of the borax solution.

Solutions of boric acid and sodium hydroxide or sodium carbonate, or other equivalents for borax may be substituted for the latter but such sources of boron typically complicate the procedure and add additional raw materials which generally increases cost. Group II metal salts comprising mineral acid salts such as chlorides and/ or nitrates and/ or sulfates of calcium, magnesium, zinc, cadmium and barium, or, acetates, lactates, and the like organic acid salts of said group II divalent metals, if sufiiciently soluble, have been found to produce insoluble I gel precipitates which are filterable and self-bonding.

Further, such salts are typically readily soluble in aqueous solution, generally low cost and easy to handle. Beryllium, strontium, mercury and radium compounds, however, generally exhibit one or more adverse characteristics such as toxic or poisonous properties, prohibitively high cost, natural radioactivity or a high degree of susceptibility to induced radioactivity and relatively long half life, etc., and therefore are not considered suitable in the present invention.

Dewatering of the aqueous slurry of borate gel precipitate and consolidation of the same may be effected by any suitable conventional means. For example, substantially any filtration means or method such as simple filtration, preferably expedited by a pressure differential such as a vacuum or high pressure head provided by a pump, press filtration comprising hydraulic or mechanical means of applying pressure, or the like may be utilized with varying degrees of economy and efliciency in extracting the excess water from the gel precipitate. Preferably a press comprising a bed having a filtering body such as a firmly supported wire screen or perforated plate and a hydraulically actuated press platen is employed, whereby strong compression may be applied to the slurry containing the borate gel precipitate to result in an efiicient high degree of dewatering and compressing or molding of said gel, particularly wherein a shaped, handleable object is desired. Of course, the press bed and platen may be such as to impart substantially any shape or configuration to the object being dewatered and/or molded. If the gel precipitate is to be utilized as a cohesive cement, dewatering should be just sufficient to provide a plastic, workable, or fiowable cohesive mass of the consistency of typical cement or mortar.

Because of their intended use, that of a shielding means or medium for noxious radiation, the hydrated borate products of this invention should be prepared at substantially the highest density practical. For example, densities of at least approximately 65 pct are desired to provide maximum resistance to radiation. Density, of course, is dependent upon dewatering and/or consolidating efiiciency and press capacity and, in general, the greater the density the more effective the shield. High densities, however, reduce the thermal insulating characteristics of the properties and where a low thermal conductivity is desired or necessary the density may be lowered.

An essential and meritorious characteristic of this hydrated borate gel precipitate or reaction product is its cohesive or self-bonding property which permits the utilization of the borate material as either a mechanically self-supporting structural shape or as a plastic cementitious or mortar-like self-adhering, cohesive mass without the addition of an extraneous or non-neutron absorbing hinder, or a retaining and supporting matrix or means which diminishes the unit volume neutron absorbing efficiency of the product. Moreover, this cohesive, selfbonding property of the hydrated borate gel materially facilitates the preparation of the borate radiation shields in that upon adequate dewatering and/or shaping of the precipitate gel slurry the material whether shaped or applied as a cementitious mass need only be dried. Drying of the dewatered and/or shaped product, if a shaped object is desired, may be effected simply by exposure to temperatures ranging from ambient up to about 1000 F., elevated temperatures in the range between 250 F. and 500 F. being preferred in that they are economical and hasten the drying. Thus, manufacture of the borate shielding products does not require the typical but expensive and involved curing or reacting of binders or other components to provide a. handleable, mechanically self-supporting structural object or shape.

Preferably, the hydrated borate gel precipitate or reaction products, whether molded or otherwise shaped into handleable, self-supporting structural shapes or simply utilized as a cohesive self-bonding cement or mortar, are reinforced with reinforcing fiber. Suitable reinforc ing fiber desirably comprises heat resistant inorganic fiber such as asbestos or an amphibole, glass, mineral wool or the like, but organic fiber such as cellulose, animal, vegetable, synthetic, etc., may sufiice for low temperature applications. Fiber may be incorporated in the gel products in substantially any amount, for example, up to approximately 30% by weight of the final product; however, excessive quantities beyond appropriate reinforcing needs, though not necessarily detrimental, obviously reduce the amount of neutron absorbing borate per unit volume and therefore may not be desirable. Approximately 510% by weight of the final product has been found generally to impart adequate strength or reinforcement for most requirements but it should be noted that the fiber content depends of course upon the intended ultimate use or strength requirements desired in the ultimate product.

It has been further found that filtration time for the borate gel precipitate can be decreased and the density of the hydrated borate gel product increased without a decrease of the boron density by the addition of an insoluble high boron containing filler such as the mineral colemanite or Gerstley borate. Gerstley borate is a tradename for a mixture of the natural minerals cole manite (Ca B O.5H O) and ulexite (NaCaB O .8I-I O). To decrease the water content of the fillers and further increase their boron content and increase their heat stability, the boron containing filler can be calcined or fritted. Suitable calcination temperatures for colemanite comprise 1100 to 1400 F. and 800 to 1100 F. for Gerstley borate. Fritting temperatures for either of these materials are in excess of 1900 F. Further, substantially any radiation attenuating material may comprise a suitable filler, for example, particulate metallic lead, iron or the like heavy elements and compounds of such materials, materials or compounds comprising a source of water, etc. The filler(s), if any, and/or the amount of the same depends, of course, upon the characteristics desired or the requirements of the particular installation or application. Fillers, however, may normally be included in any amount up to approximately 70% by weight of the total.

Hydrogen is also a good absorbent and barrier for neutrons, and water, being a ready and economical source of hydrogen therefore may be a desirable component of a borate gel product. For example, a substantial water content is advantageous where shielding fast neutrons is also desirable or necessary. Other applications, however, particularly wherever there is a possibility that liquid sodium metal might contact the borate shield, require a substantially water free product and this may be achieved simply by firing the dried borate products at temperatures up to about 1000 F. Temperatures in the region of 850 to 950 F. normally effect adequate water removal for safe use of the product with sodium metal containing installations.

The hydrated borate compositions comprising this improved radiation shield efiectively resist all typical deleterious elements or conditions such as radiation, high temperatures and the like normally present in or about reactors, cyclotrons, radioactive materials, etc. For example, shaped hydrated borate products prepared in accordance with this invention resist soaking temperatures up to 1500 F. and repeated exposure of one side to temperatures of 1000 F. without any indication of cracking or spalling. Moreover, these products withstand neutron flux equivalent to 2.4 1O nvt and gamma flux equivalent to 2 10 m.e.v./cm. /sec. without affecting their resistance to crushing or suffering any damage or deterioration.

The following examples illustrate typical hydrated borate gel compositions, products thereof and methods of manufacturing the same. It is to be understood that the specific compositions of the borate gels are exemplary and are not to be construed to limit the invention to the proportions of reactants or the reaction conditions specified in the examples.

Example I Borax in amount of 81.6 lbs. was dissolved in 40 gals. of water maintained at temperature of approximately 140 F. Upon dissolution of all the borax, 13 lbs. of asbestos fiber were added to the solution which was constantly maintained at a temperature of at least F. An aqueous solution of calcium chloride was prepared by dissolving 31.5 lbs. of anhydrous calcium chloride (CaCl in 3 gals. of water at room temperature. The calcium chloride solution was then added to the borax solution-fiber suspension and the resulting gel was stirred to expedite the reaction. 122.3 lbs. of the mineral colemanite, fired at a temperature of approximately 1,350 F., was then added to the gel-fiber suspension and mixed until uniform. The thus prepared slurry was molded into blocks by pressing the same between screens. The resulting shaped calcium borate gel material had the following properties:

Density lbs./cu. ft 73.9

B 0 percent 42.2

Boron density lbs./cu. ft 9.8

Example 11 Density s/cu. ft 49 Fiber percent 20.3 B 0 density lbs./cu. ft 17.8 Boron density lbs/cu. ft 5.5 Boron weight percentfl 11.2

Accounting for 9.9 lbs/cu. ft. of the density.

Example III A hydrated calcium borate gel having a l to 1 0210 to B mol ratio was prepared by combining an aqueous borax solution comprising 190.5 grams of borax in 1,000 m1. of hot (158 F.) water and a calcium chloride solution comprising 111.0 grams of anhydrous calcium chloride dissolved in 300 ml. of water. Both solutions were cooled to 95 F. and mixed. To the resulting gel precipitate 18 grams of chrysotile fiber were added and upon thorough mixing the fiber-borate slurry was placed in a 6" x 6" press with a perforated platen and formed into a block at a pressure of 15,000 lbs. Upon oven drying at 248 F. for 24 hours, the resulting block exhibited the following properties:

Density lbs./cu. ft 38.0

Fiber density -lbs./cu. it 3.1

B 0 density lbs./ cu. ft 15.0

Boron density lbs/cu. ft 4.7

Boron weight percent 12.4

Example IV A calcium borate gel having a 1 to 2 CaO to B 0 mol ratio was prepared in the same manner as Example III by utilizing /2 the quantity of calcium chloride solution specified in Example III, i.e., 55.5 grams of an anhydrous calcium chloride in 150 ml. of water. Blocks so prepared exhibited the following properties:

Density lbs./cu. ft 37.0

Fiber density lbs./cu. ft-- 34 B 0 density lbs./cu. ft 17.6

Boron density lbs./ cu. 'ft 5.5

Boron weight percent 14.9

1 Example V A barium borate gel product was prepared by combining a borax solution comprising 190.5 grams of borax in 1,000 ml. of hot (158 F.) water and a barium chloride solution comprising 244 grams of barium chloride (BaCl .2H O) dissolved in 600 ml. of hot (158 F.) water. Both solutions were cooled to 95 F. prior to mixing. 20 grams of chrysotile asbestos were added to the thus formed barium borate gel precipitate and after thorough mixing the fiber-borate slurry was pressed in a 6" x 6" press with a perforated platen and formed into a block using a pressure of 13,000 lbs. The pressed block upon oven drying at 248 F. for 24 hours exhibited the following properties:

Density lbs./cu. ft 52 Fiber percent 10.1

B 0 density lbs./cu. ft 13.8

Boron density lbs./cu. ft 4.3

Boron weight percent 8.3

Example VI A zinc borate gel product was prepared by combining a borax solution comprising 100.0 grams of borax in 500 ml. of hot (155 F.) water and a zinc sulfate solution comprising 112 grams of zinc sulfate (ZnSO -7H O) in 200 ml. of hot (155 F.) water. Both solutions were cooled to 90 F. prior to mixing. 10 grams of chrysotile asbestos were added to the thus formed zinc borate gel precipitate and after thorough mixing the fiber-borate slurry was dewatered and shaped by filtration and the cake dried at 250 F. for 24 hours. On drying a firm cake was obtained.

Example VII A cadmium borate gel product was prepared by combining a borax solution comprising 381 grams of borax in 1,000 ml. of hot (158 F.) water and a cadmium chloride solution comprising 183.3 grams of cadmium chloride (CdCl in 100 ml. of hot (158 F.) water. Both solutions were cooled to 90 F. prior to mixing. 10 grams of chrysotile asbestos were added to the thus formed cadmium borate gel precipitate and after thorough mixing the fiber-borate slurry was dewatered and shaped 8 by filtration and the cake dried at 250 F. for 24 hours. On drying a rigid well bonded product was obtained.

Example VIII A calcium borate gel product was prepared by combining a borax solution comprising 66.2 grams of borax in 400 ml. of hot (155 F.) water and a calcium nitrate solution comprising 41 grams of calcium nitrate (CaNO .4H O) in 100 ml. hot (155 F.) water. Both solutions were cooled to F. prior to mixing. The calcium borate precipitate was dewatered by filtering. On drying at 250 F. for 24 hours a firm cake was produced.

Example IX Another calcium borate gel was similarly prepared by mixing a borax solution comprising 190.5 grams of borax dissolved in 1,000 ml. of hot (158 F.) water and a calcium nitrate solution comprising 118.1 grams of calcium nitrate (CaNO .4H O) in 300 ml. of hot (158 F.) water. Both solutions were cooled to F. prior to mixing. 15 grams of chrysotile asbestos fiber were added to the thus formed calcium borate gel and after thorough mixing the fiber-borate slurry was dewatered and shaped by filtration and the resulting bodies dried at 248 F. for 24 hours. The properties of these bodies were not unlike those prepared from calcium chloride.

The following examples illustrate the use of typical organic acid salts of suitable group II divalent metals, and as set forth hereinbefore, these examples are merely exemplary of this invention and are not to be construed to limit the invention to the specified reactants, their proportions or reaction conditions.

Example X A calcium borate gel product was prepared from an organic acid salt by combining at a temperature of about 150 F. a solution of 8.8 grams of calcium acetate (Ca(C H O .H O) in 50 ml. of water and a solution of 19.0 grams of borax dissolved in 250 ml. of hot (140 F.) Water. The resulting gel precipitate was filtered and consolidated to a density of approximately 20 lbs./ cu. ft. and dried at 250 F. for 24 hours. The product was handleable and structurally strong exhibiting physical properties comparable to the hydrated borate products of foregoing examples.

Example XI A second calcium borate gel product was prepared from a calcium lactate acid salt by mixing, at a temperature of about 150 F., 15.4 grams of calcium lactate in 200 ml. of Water with 19.0 grams of borax dissolved in ml. of hot F.) water. The gel precipitate formed was processed as before, i.e., filtered and consolidated to an approximately 20 lbs/cu. ft. density and dried for 24 hours at 250 F., and, like the product of the foregoing example, was handleable, structurally strong and similar in other physical properties.

Example XII A cadmium borate gel product was produced by effecting mixing, at temperatures of about F., of a borax solution comprising 19.1 grams of borax dissolved in 100 ml. of hot (140 F.) water and a cadmium acetate solution comprising 13.4 grams of cadmium acetate in 30 ml. of water. The thus formed gel precipitate was dewatered by filtering and consolidated to a density of about 20 lbs/cu. ft. and the cake dried at 250 F. for 24 hours. The dried product was firm, handleable and physically comparable to the products of inorganic reactants.

Example XIII A zinc borate gel product was also prepared by mixing a borax solution, comprising 19.1 grams of borax dissolved in 100 ml. of hot (140" F.) water, with an acid salt of Zinc, comprising 11.0 grams of zinc acetate (Z11 (C2H302) 2.2H20) dissolved in 30 m1. of water, at a temperature of about 150 F. Dewatering and consolidation of the precipitated gel product was effected by filtering and hand pressing until a density of approximately 20 lbs./cu. ft. was reached. The resulting firm cake, upon drying at 250 F. for 24 hours, was handleable, rigid, structurally strong and, like the foregoing borate gel products produced from an organic component, exhibited physical properties substantially identical to those prepared entirely from inorganic reactants.

Although organic acid salts of suitable group II divalent metals permit the preparation of advantageous and useful products as is apparent from the foregoing examples, their use is not preferred primarily for reasons of economy.

For reasons clearly apparent from the foregoing disclosure thee terms soluble or solubility as used throughout this specification and the appended claims are intended to denote or define the capability of at least approximately 1 part by weight of a solute to mix (dissolve) with 3 parts by Weight of an aqueous liquid (solvent) to form a homogeneous mixture (solution). In other Words for practical, efficient and economical practice of this invention, the mineral salts of the divalent metals should have a solubility of at least approximately 35 grams per 100 ml. of water and the scope of this invention as defined by the claims should be so construed.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

What I claim is:

1. The method of preparing structural borate neutron shielding material consisting essentially of self-bonding, Water insoluble hydrated borate gel, which comprises forming a water insoluble hydrated borate gel precipitate by combining, in aqueous solution, borax and Water soluble acid salts of a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about l-2 mols of B for each mol of divalent metal oxide and at temperatures within the range of approximately 60-200 F.

2. The method of preparing structural borate neutron shielding material consisting essentially of self-bonding, water insoluble hydrated borate gel, which comprises forming a water insoluble hydrated borate gel precipitate by combining, in aqueous solution, borax and Water soluble organic acid salts of a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B 0 for each mol of divalent metal oxide and at temperatures within the range of approximately 60200 F.

3. The method of preparing structural borate neutron shielding material consisting essentially of self-bonding, water insoluble hydrated borate gel, which comprises forming a water insoluble hydrated borate gel precipitate by combining, in aqueous solution, borax and water soluble mineral acid salts of a group H divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about l-2 mols of B 0 for each mol of divalent metal oxide and at temperatures within the range of approximately 60200 F.

4. The method of preparing structural borate neutron shielding material consisting essentially of self-bonding, water insoluble hydrated borate gel, which comprises forming a water insoluble hydrated borate gel precipitate by combining, in aqueous solution, borax and water soluble salts of a mineral acid selected from the group consisting of hydrochloric, nitric, and sulfuric, and mixtures thereof, and a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B 0 for each mol of divalent metal oxide and at temperatures within the range of approximately 60200 F.

5. The method of preparing structural borate neutron shielding material consisting essentially of self-bonding, water insoluble hydrated borate gel reinforced with fiber, which comprises forming a water insoluble hydrated borate gel precipitate by combining, in aqueous solution, borax and water soluble salts of a mineral acid selected from the group consisting of hydrochloric, nitric, and sulfuric, and mixtures thereof, and a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and Zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B 0 for each mol of divalent metal oxide and at temperatures within the range of approximately 60200 F., and providing throughout the said gel precipitate reinforcing fiber in amount up to approximately 30% by weight of the material.

6. The method of preparing structural borate neutron shielding material consisting essentially of self-bonding, water insoluble hydrated borate gel containing particulate filler of radiation attenuating materials, which comprises forming a water insoluble hydrated borate gel precipitate by combining, in aqueous solution, borax and water soluble salts of a mineral acid selected from the group consisting of hydrochloric, nitric, and sulfuric, and mixtures thereof, and a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B 0 for each mol of divalent metal oxide and at temperatures within the range of approximately 60200 F., and providing throughout the said gel precipitate particulate filler comprising radiation attenuating materials in amount up to approximately 70% by weight of the material.

7. The method of preparing structural borate neutron shielding material consisting essentially of self-bonding, water insoluble hydrated borate gel reinforced with fiber and containing particulate filler of radiation attenuating materials, which comprises forming a water insoluble hydrated borate gel precipitate by combining, in aqueous solution, borax and water soluble salts of a mineral acid selected from the group consisting of hydrochloric, nitric, and sulfuric, and mixtures thereof, and a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B 0 for each mol of divalent metal oxide and at temperatures within the range of approximately 60-200 F., and providing throughout the said gel precipitate reinforcing fiber in amount up to approximately 30% by weight of the material and particulate filler comprising radiation attenuating materials in amount up to approximately 70% by weight of the material.

8. The method of preparing structural borate neutron shielding material consisting essentially of self-bonding, Water insoluble hydrated borate gel reinforced with fiber and containing particulate filler of radiation attenuating materials, which comprises forming a water insoluble hydrated borate gel precipitate by combining, in aqueous solution, borax and water soluble salts of a mineral acid selected from the group consisting of hydrochloric, nitric, and sulfuric, and mixtures thereof, and a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B 0 for each mol of divalent metal oxide and at temperatures within the range of approximately -190 F., providing throughout the said 11 gel precipitate inorganic reinforcing fiber in amount up to approximately 30% by Weight of the material and particulate filler comprising radiation attenuating materials in amount up to approximately 70% by welght of the material, and compressing the fiber reinforced gel precipitate to dewater and shape the same.

9. The method of preparing structural borate neutron shielding material consisting essentially of self-bonding, water insoluble hydrated borate gel reinforced with inorganic fiber, which comprises forming a water insoluble hydrated borate gel precipitate by combining, in aqueous solution, borax and water soluble salts of a mineral acid selected from the group consisting of hydrochloric, n1- tric, and sulfuric, and mixtures thereof, and a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B for each mol of divalent metal oxide and at a temperature of approximately 140 F., providing throughout the said gel precipitate inorganic reinforcing fiber in amount of approximately 10% by weight of the material, and compressing the fiber reinforced gel precipitate to dewater, shape and consolidate the same to a density to at least about 65 lbs. per cu. ft.

10. The method of preparing structural borate neutron shielding material consisting essentially of self-bonding, water insoluble hydrated borate gel reinforced with inorganic fiber and containing particulate filler of radiation attenuating materials, which comprises forming a Water insoluble hydrated borate gel precipitate by combining, in aqueous solution, borax and water soluble salts of a mineral acid selected from the group consisting of hydrochloric, nitric, and sulfuric, and mixtures thereof, and a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 12 mols of B 0 for each mol of divalent metal oxide and at a temperature of approximately 140 F., providing throughout the said gel precipitate inorganic reinforcing fiber in amount of approximately 5-10% by weight of the material and particulate filler comprising radiation attenuating materials in amount up to approximately 70% by Weight of the material, and compressing the fiber reinforced, filled, gel precipitate to dewater, shapeand consolidate the same to a density of at least about 65 lbs. per cu. ft.

11. A structural borate neutron shielding material consisting essentially of the self-bonding, Water insoluble borate gel precipitate reaction product of combining, in aqueous solution, borax and water soluble acid salts of a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B 0 for each mol of divalent metal oxide and at temperatures within the range of approximately 60200 F.

12. A structural borate neutron shielding material consisting essentially of the inorganic fiber reinforced, self bonding, water insoluble borate gel precipitate reaction product of combining, in aqueous solution, borax and water soluble acid salts of a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B 0 for each mol of divalent metal oxide and at temperatures within the range of approximately 200 F., and reinforcing inorganic fiber in amount up to approximately 30% by weight of the material.

13. A structural borate neutron shielding material consisting essentially of the filled, self-bonding, water insoluble borate gel precipitate reaction product of combining, in aqueous solution, borax and water soluble acid salts of a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B 0 for each mol of divalent metal oxide and at temperatures within the range of approximately 60200 F., and particulate filler of radiation attenuating materials in amount up to approximately by Weight of the material.

14. A structural borate neutron of shielding material consisting essentially of the inorganic fiber reinforced, filled, self-bonding, water insoluble borate gel precipitate reaction product of combining, in aqueous solution, borax and water soluble acid salts of a group II divalent metal selected from the group consisting of calcium, barium, magnesium, cadmium, and zinc, and mixtures thereof, in an approximate ratio, on an oxide basis, of about 1-2 mols of B 0 for each mol of divalent metal oxide and at a temperature within the range of approximately 60-200 F., and reinforcing inorganic fiber in amount up to approximately 30% by Weight of the material and particulate filler of radiation attenuating materials in amount up to approximately 70% by weight of the material.

References Cited in the file of this patent UNITED STATES PATENTS 2,405,366 Myhren et al. Aug. 6, 1946 2,607,658 Govett et al. Aug. 19, 1952 2,716,705 Zinn Aug. 30, 1955 2,717,240 Frommuller Sept. 6, 1955 2,726,339 Borst Dec. 6, 1955 2,727,996 Rockwell Dec. 20, 1955 2,747,105 Fitzgerald et a1 May 22, 1956 2,796,411 Zirkle June 18, 1957 2,836,500 Weidman May 27, 1958 OTHER REFERENCES Mellor: A Comprehensive Treatise on Inorganic and Theoretical Chemistry, vol. V, 1924, pp. 87-101, pub. Longmans, Green, and Co., New York.

Rose: The Condensed Chemical Dictionary, 5th ed., 1956, pp. 115, pub. Reinhold Pub. Corp, New York.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 l26,352 March 24 1964 Laurence Ra Blair et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1 line 13, strike out "material"; column 3 line 5l for "temperatures" read temperature column 6, line 60, for "chrysolite" read chrysotile column 9, line 20 for "thee" read the Signed and sealed this 21st day of July 1964i (SEAL) Attest:

ESTDN G. JOHNSON EDWARD J BRENNER Attesting OffiCGI' Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 126,352 March 24in 1964 Laurence H. Blair et all, It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 13, strike out "material"; column 3 line 51 for "temperatures" read temperature column 6 line 60 for "chrysolite" read chrysotile column 9 line 2O for "thee" read the Signed and sealed this 21st day of July 1964,

(SEAL) Attest:

ESTQN G. JDHNSON EDWARD J. BRENNER Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE- CERTIFICATE OF CORRECTION Patent No, 3 126352 March 24 1964 Laurence H, Blair et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1 line 13 strike out "material"; column 3 line 51 for "temperatures" read temperature column 6 line 60 for "chrysolite" read chrysotile column 9,, line 2O for thee read the "q Signed and sealed this 21st day of July 1964a (SEAL) Attest:

EsToN ea JoHNsoN EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. THE METHOD OF PREPARING STRUCTURAL BORATE NEUTRON SHIELDING MATERIAL CONSISTING ESSENTIALLY OF SELF-BONDING, WATER INSOLUBLE HYDRATED BORATE GEL, WHICH COMPRISES FORMING A WATER INSOLUBLE HYDRATED BORATE GEL PRECIPITATE BY COMBINING, IN AQUEOUS SOLUTION, BORAX AND WATER SOLUBLE ACID SALTS OF A GROUP II DIVALENT METAL SELECTED FROM THE GROUP CONSISTING OF CALCIUM, BARIUM, MAGNESIUM, CADMIUM, AND ZINC, AND MIXTURES THEREOF, IN AN APPROXIMATE RATIO, ON AN OXIDE BASIS, OF ABOUT 1-2 MOLS OF B2O3 FOR EACH MOLE OF DIVALENT METAL OXIDE AND AT TEMPERATURES WITHIN THE RANGE OF APPROXIMATELY 60-200*F.
 11. A STRUCTURAL BORATE NEUTRON SHIELDING MATERIAL CONSISTING ESSENTIALLY OF THE SELF-BONDING, WATER INSOLUBLE BORATE GEL PRECIPITATE REACTION PRODUCT OF COMBINING, IN AQUEOUS SOLUTION, BORAX AND WATER SOLUBLE ACID SALTS OF A GROUP II DIVALENT METAL SELECTED FROM THE GROUP CONSISTING OF CALCIUM, BARIUM, MAGNESIUM, CADMIUM, AND ZINC, AND MIXTURES THEREOF, IN AN APPROXIMATE RATIO, ON AN OXIDE BASIS, OF ABOUT 1-2 MOLS OF B2O3 FOR EACH MOL OF DIVALENT METAL OXIDE AND AT TEMPERATURES WITHIN THE RANGE OF APPROXIMATELY 60-200*F. 